pandas 某一列不重复的值有多少

以o2o大赛的数据为例

df_new = df[['User_id','Merchant_id']]

df_new_1 = df_new.groupby(['User_id'])['Merchant_id'].nunique()

在同一个'User_id'下，'Merchant_id'有多少个

df_new_1 = df_new.groupby(['User_id'])['Merchant_id'].value_counts()

Name: Merchant_id, dtype: int64

df_new_1 = df_new.groupby(['User_id'])['Merchant_id'].unique()

返回具体的unique值

Series.nunique(dropna=True)[source]

Parameters:	dropna : boolean, default True Don’t include NaN in the count.
Returns:	nunique : int

Return number of unique elements in the object.

Excludes NA values by default

源码

def nunique ( self , dropna = True ):

"""

Return number of unique elements in the object.

Excludes NA values by default.

Parameters

----------

dropna : boolean, default True

Don't include NaN in the count.

Returns

-------

nunique : int

"""

uniqs = self .unique()

n = len (uniqs)

if dropna and isna(uniqs).any():

n -= 1

return n

.